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Applied Bionics and Biomechanics
Volume 5, Issue 3, Pages 135-147
http://dx.doi.org/10.1080/11762320802221074

No Need for a Body Model: Positive Velocity Feedback for the Control of an 18-DOF Robot Walker

Josef Schmitz, Axel Schneider, Malte Schilling, and Holk Cruse

Department for Biological Cybernetics, Faculty of Biology, University of Bielefeld, P.O. Box 10 01 31, D-33501 Bielefeld, Germany

Received 22 May 2008

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In a multilegged walking robot several legs usually have ground contact and thereby form a closed kinematic chain. The control of such a system is generally assumed to require the explicit calculation of the body kinematics. Such a computation requires knowledge concerning all relevant joint angles as well as the segment lengths. Here, we propose a biologically inspired solution that does not need such a body model. This is done by using implicit communication through the body mechanics (embodiment) and a local positive velocity feedback strategy (LPVF) on the single joint level. In this control scheme the locally measured joint velocity of an elastic joint is fed into the same joint during the next time step to maintain the movement. At the same time, an additional part of this joint controller observes the mechanical joint power to confine the positive feedback. This solution does not depend on changes of the geometry, e.g. length of individual segments, and allows for a simple solution of negotiation of curves. The principle is tested in a dynamics simulation on a six-legged walker and, for the first time, also on a real robot.